1. Field of the Invention
The invention relates to a catalyst for hydrogenation of oxalic ester to ethanol, a method for preparing the catalyst and a method for using the same.
2. Description of the Related Art
Traditional technology for production of ethanol mainly includes ethylene hydration and biomass fermentation. Ethylene hydration route uses ethylene, a cracked product of petroleum, as raw material to yield ethanol by hydration of ethylene. Biological fermentation refers to the use of agricultural products which contain a variety of sugars (disaccharide), starches (polysaccharides), cellulose (hexose), forestry by-products and wild plants as raw materials. Polysaccharides and disaccharides are first hydrolyzed to yield monosaccharide and monosaccharide is then fermented to produce ethanol.
Due to resource conditions, the large-scale use of sugar or corn to produce fuel ethanol is limited and the technology with cellulose as the raw material to produce ethanol is not yet mature. Production of ethanol from synthesis gas has attracted great attention as synthesis gas can be acquired from coal, natural gas, or biomass resources. The production of ethanol from synthesis gas includes first preparing two carbon products such as acetaldehyde, ethanol, ethyl acetate and acetic acid over Rh/SiO2 catalyst under 3-10 MPa and 300° C., and then the by-products such as acetaldehyde, ethyl acetate and acetic acid are further converted to ethanol through hydrogenation over Cu/SiO2, Pd—Fe/SiO2 or Cu—Zn—Al—Mg—Mo catalysts. Due to the rigorous technical conditions, poor stability and low selectivity of the catalyst, the method cannot be applied in large scale up to now.
Conventional copper-based catalysts for hydrogenation of acetate to ethanol have a low conversion rate and the reaction efficiency is quite low, and the stability data was not reported. The catalytic stability is critical for copper catalysts because metallic particles on the surface of catalyst are prone to aggregate and sinter at high temperature. Therefore, the development of copper-based catalyst with high resistance to sintering, high activity and selectivity at high temperature for hydrogenation of oxalic ester is one of the key technologies.